Stub for pyclbr.py (#487)

* Stub for pyclbr.pyi

* Quote opaque type with ""

stdlib/3/pyclbr.pyi

@@ -0,0 +1,40 @@
+from typing import List, Union, Sequence, Optional, Dict
+
+
+class Class:
+    module = ...  # type: str
+    name = ...  # type: str
+    super = Optional[List[Union["Class", str]]]
+    methods = ...  # type: Dict[str, int]
+    file = ...  # type: int
+    lineno = ...  # type: int
+
+    def __init__(self,
+                 module: str,
+                 name: str,
+                 super: Optional[List[Union["Class", str]]],
+                 file: str,
+                 lineno: int) -> None: ...
+
+
+class Function:
+    module = ...  # type: str
+    name = ...  # type: str
+    file = ...  # type: int
+    lineno = ...  # type: int
+
+    def __init__(self,
+                 module: str,
+                 name: str,
+                 file: str,
+                 lineno: int) -> None: ...
+
+
+def readmodule(module: str,
+               path: Optional[Sequence[str]] = ...
+               ) -> Dict[str, Class]: ...
+
+
+def readmodule_ex(module: str,
+                  path: Optional[Sequence[str]] = ...
+                  ) -> Dict[str, Union[Class, Function, List[str]]]: ...